Gaseous discharge device



Aug. 1, 1950 A. H. REEVES GASEOUS DISCHARGE DEVICE Filed 001;. 3, 1947ATTORNEY Patented Aug. 1, 1950 7 7 7 2,516,915 desirous niscnARGE DEVICE.AlecHarley Reeves,iLondonpEngland, assignor -to International StandardElectric Corporation, New York, N. Y., a corporation of DelawareApplication OctoberB, 194.7, Serial No. 777,815

UNITED STATES Pints-r *In Great Britain October 3,1946 ioclaims. (01.315-323) This invention relates to the use of .coldcathode gaseousdischarge tubes having a plurality of .discharge gaps such as tubes ofthe type described in application Serial No. 763,655, filedJuly 25,

Tubes described inthe .said application comprise an arrayof three ormore dischargegaps 50 arranged that upon a discharge beinginitiated atone of these gaps, ionisation fromthedischarge lowers the minimum=voltage at whichan adjacent gap will discharge due toionisationof thegas in the latter gap due to ithe discharge inthe former. Whenpulses'areapplied in common to the gaps of such a tube, successive pulses causethe firing of successive gaps in the tube till all have discharged. 7 7

A given gap,usually the firstyrnaybe. arranged so that thepulsevoltagecauses it to .fire in the absence ofgas ionisationand afirst pulse is applied to the tube when it is de-ionised, causing thisgap onlytoiire. 7 7 7 7.Such a gap is called the startinggap and theefiect'may be obtained by various methods of which three may bementioned:

so that gas ionisation from this discharge permanently primesthestarting gap but not other gaps of the tube. Such an auxiliary gap iscalled a pilot gap.

In operating tubes of this type a constant standing potential can beapplied to all the, gaps sufficient to maintain a, discharge, onceinitiated, but insufiicient to initiate a discharge by itself, even whenionisation is present.

When pulses are applie to the gaps'of such a tube the gaps will fire insuccession and continue discharging throughout the remainder ofthesequence of dischargesin the tube.

It is however, possible to operate the tube without amaintainingpotential as willbe described later. L

Where itis' required to apply 'a continuingsuccession of pulsesto thetube itis necessarythat all "discharges in the' tube shallfbeextinguished and thatthe'gas' in the tube' shall become deiorgisedbefore'a further pulse is applied to the ue. This further pulse ;Wil1then fire, the starting gap and the sequence of discharges willre-commence. Theprocesscan :then be :repeatedagain andiagainn .7 7. 7 77 Tubes .01 the typeito whichxthe .invention relates may, bebarranged sothat gaps .fired 7 .by. a train of pulses automatically extinguishbetween pulses, or so that gaps fired by a train of pulses continuetodischargebetween pulses.

. .Whena tube is77arrang'edlso 7that .thedischarge is maintained betweenpulses various 77means 7 of extinguishing theedischarges are possiblesome of which aredcscribed latch... 7 7 7,

1 After extinguishznent ofithe dischargesitheigas in the, gaps (otherthanitheistartinglgap, where a pilotgap is used)- must 77bccomedeionised before the application of a further pulse.Ifithis7deionisation has not prooeededto asuflicientextent, 7 there is77a.;risk .of .gaps other than thestarting gap being fired by thefurther pulse applied to thetube... 7 7 g 7 ,7

7 Therewill be a;critical .,frequency below which the inter-pulse77interval -.in.. a777c0ntinu0us sequence of regularlysspaced ipulsesinlong enoughgto permit the tube to become deionised between pulsesbutabove which the tube will fail to operate correctly. 7 77 .7 7

The object of the present invention is to enable pulse .irequenciesto77be7 used7.higher than this critical frequency without upsetting theoperationofthetuba.

7 According to, its 7 principal, feature therefore, the inventionconsists. of :7a1deyice.:responsive .to recurring ,pulses iOf;electrical 7-,encrgy which comprises a cold cathodegas discharge :tubehaving three or more ,dischargegaps adapted to .fire succession inallpredeterminedorder onzthe application of pulses tothe,saidgapsincommon, ionisation from a discharge in oneqgap loweringthevoltage necessary to fire the next adjoining unfired gap andso .prirningthesaid adjoining gap, inwhich when all the sapshave been firedin turn,all 7 discharges in these ,gaps' automatically extin guish or areextinguished, and which cornprises means for 7preventing ofnelor'mor'epulses immediately succeedingi the'pulse'7 which causedgthe lastof the saidga'ps Ito firefrom firing any of the said gaps 'onth'e gu sein order to provide time for all thesaid gaps fin the tube toextinguishand to deionise to atleast a predetermined extent so that thenext pulse allowed to afiect the tube will fire the'first gap in thesaid predetermined 'order and no other gapi Certain embodiments of theinvention will now be described in relation to the accompanying drawingsin which:

Fig. 1 is a circuit diagram of one embodiment of the invention.

Fig. 2 is a circuit diagram of another embodiment of the invention. I I

The circuit of Fig. 1 forms part of the subject matter of our co-pendingapplication Serial No. 777,816, filed October 3, 1947, now Patent No.2,505,006.

In this figure a gaseous discharge tube 1 has a common anode 2consisting of a, straight rod wire or strip and having eight cathodepoints adjacent to it forming eight discharge gaps, 3, 4, 5,6,1,8,9andll3.

Gap 3 is the starting gap and is shown somewhat shorter than the rest.The cathode of this gap is shown as being separately led out of the tubebut this is not essential. The cathodes of gaps 4, 5, 6, 1, 8 and 9 arein the form of projections from a common supporting rod. The cathode ofgap I is separatel led out of the tube. I

The cathode of gaps B to 9 may alternatively take any of the formsdescribed in my application first above mentioned, for instance acorrugated strip may be used, the peaks of the corrugations towards theanode defining the various gaps.

A voltage is applied across all the gaps in common from battery H, inthe case of the anode, through a resistance 12, in the case of theoathode of the starting gap 3, through resistance I3,

in the case of the cathodes of gaps 4 to 9 through resistance [4 and inthe case of the cathode of gap I!) through resistance l5, and in certaincases also through apparatus connected to output terminals I6.

Condenser I'll is a feed condenser through which recurrent pulsesapplied across terminals 18 are fed to the tube.

The startin gap 3 is ensured of striking from a first pulse when the gasin the gap is deionised by being shorter than the rest, and thisshortness is exaggerated in the figure so that it may be readilyapparent.

If other means of ensuring the firing of the starting gap from a firstpulse were resorted to, gap 3 could be the same size as the other gaps,and resistance i3 may be considered as representing a circuit forapplying a bias across the gap. In the arrangement illustrated in theFigure 1 resistance 13 could be omitted and the cathode of gap 3 couldbe fed through resistance 14.

On pulses being applied at i8, first the starting gap 3 and then theremaining gaps, will fire in succession from successive pulses,discharges being maintained after firing by reason of battery ll whichis adjusted so that it will not initiate a discharge but will maintain adischargeonce initiated.

The cathode of gap may have a somewhat larger area than the othercathodes. When this gap fires, a surge of current passes through thisgap discharging condenser 19, which at other times is charged to avoltage somewhat below that of the battery H plus the pulse voltage.

This lowers the anode-to-cathode voltage momentarily, below thatrequired to maintain the discharges, which are therefore extinguished.

The time during which the voltage remains lowered depends upon the timeconstants of condenser 19, resistance I 2, and resistance Hand also, tosome extent the circuits if any attached to terminals 16.

Where the frequency and spacing of the pulses applied to terminals i8 issuch that the tube can become deionised in the interval between twoadjacent pulses, the time constant of the voltage lowering circuit willbe chosen to be similar to the pulse interval so that by the time ofarrival the next pulse after that which fired gap In, theinter-electrode voltage will have restored to approximately that ofbattery II.

If, however, with the same circuit values, the pulse rate is increased,the inter-electrode voltage will not have reached that of battery H atthe time of the next pulse after that which fired gap l0, and if thatvoltage at such time is below a critical value, the starting gap willnot fire oif this next pulse and may miss several pulses, according tothe amount by which the pulse rate is increased. f,

In this way, the tube will measure ofi pulses greater in number than thenumber of its discharge gaps.

This efiect may be exploited to obtain two advantages; first, to enablea pulse rate to be used such that de-ionisation cannot be completedbetween successive pulses and secondly, to enable counting to take placeto a radix-greater than the number of gaps in the tube.

The circuit of Fig. 1 may be used as a counter, with an externalcounting circuit connected in series across terminals [6 or in parallelacross terminals 2:) (terminals 16 being short-circuited in the lattercase) and will record the successive discharges in gap in.

There is sometimes difiiculty in securing a suificiently stableinter-electrode voltage in the tube owing to the varying currents drawnas different numbers of gaps are discharging from time to time.

Accordingly, it is advisable to insert choke 2| and rectifier 22,connected between the anode and a tapping on the battery Hi The tappingis chosen so that rectifier 22 is just non-conducting when all gaps arefiring, that is to say, when the voltage drop in [2 is at its maximum.

When fewer gaps are firing 22 is more conducting due to the anode beingmore positive than the tapping point on H, making a conducting paththrough 2| and 22 from the anode to the said tapping point which tendsto stabilise the anode voltage at a value in the vicinity of that of thesaid tapping point.

When gap is fires, however, the surge of current causes a furthervoltage drop in !2 which cuts off the rectifier, so that the drop involtage required to extinguish the tube, is not defeated by thestabilising circuit 2 I, 22.

The choke 2! is required principally to prevent the bypassing of thepulses through the rectifier and battery, though it is also anadditional precaution against the loss of the quenching surge. In thearrangement illustrated in Fig. 2 the prin ciple of preventing the tubefrom firing from a pulse or pulses after that which fired the last gap,is carried a stage further by switching both pulses and maintainingbattery from the tube in question and transferring them to anothersimilar tube which commences a firing sequence where the first tube leftoff, after the completion of which, the pulses are again applied to thefirst tube, the two tubes working alternately.

In this arrangement the number of pulses during which a tube is dormantis precisely counted out by anothertube instead of being timed.

aura-e In Fig. 2 atube 23 of the type describedin our copendingapplication, first above mentioned, has an anode 2 4 in theform of awire, strip or plate, and acathode array at with individual cathodes inthe form of rods mounted on a common busbar 26 in the form of a comb.All the array gaps are of equal-length and aseparatepriming gap 2 isincluded to prime the starting gap. 28 at theleft-hand end: of thearray. A separate oath 0de29 is provided at the other end and is spacedsimilarly to the other array gaps as regards both gap length andseparation from its neighbour. Tube 30 is similar in function to tube23,-but.di-iferent forms of electrode are shownto illustrate analternative tube construction. Anode 34 is again a wire, strip or plate,but cathode array 32- consists of a serrated metallic strip, coated withalumina or similar substance except at the tips of the saw teeth. At oneend, the first tooth on 32 co-operates with a separate anode to providea priming gap 33 and starting gap 34. At the other end. a separatecathode :35 is provided, similarlyto 23 in tube 23. Cathode arrays 25and tzare'shown connected to ground and anodes at and Sal are connectedvia separate leads 3B and i i to the respective side contacts a: of apolarized relay A which has opposed windings and is adjusted to be sidestable. Leads 36 and Bl are also connected through individual pulseblocking chokes 38 and 38to the side contacts atohrelay A and throughleak resistances til,

to ground. With the armatures of (ti and (1'2 in the position shown,anode 24 is connected through condenser 13.2 to pulse input terminal 43and through choke at to the positive pole of battery flit, the negativepole of which is grounded. Anode 3:1 is open circuited except for itsleak connection to ground. Priming gaps 2'1 and 33 are connected throughvariable resistances Q5 and 45 respectively across batteries .4! andill. The output cathodes 29 and 3'5 are connected through the opposingwindings of relay A to recording device 49:. It should be emphasizedthat the functions of relay Aand recording device ct could be carriedout b electronic means such as circuits i tubes 23 and 39 without,however, causing any gap to fire (other than the starting gap) even whenpulses from terminal it are applied to the respective anodes.Resistances t5 and may be adjusted to control the priming currents ofgaps 2i and 33. Assume, now that positive pulses are applied to terminal63, the relay contacts at a! and a2 being in the condition indicated inthe figure. The first pulse will fire gap 28, which Willremaindischarging under the influence of the maintaining voltage from batteryt l after the pulse has passed. By the time the second pulse arrives,the gas in the next gap is ionised by the discharge recently started atgap 28, and this second pulse added to the voltage from battery id willfire the gap adjacent to 28, the third ulse will fire the next gap, andso on until discharge occurs at cathode 29. The discharge currentthrough cathode 29 actuates relay A and also recording device 49 so thatthe completion .oflthe firstdischarge-sequence is recorded. Due

to the operationof relay anodeuzlris discom nected from terminal 43 andbattery .44: Dis= charge'sat all gaps of tube '23 except the'priming gap2l will thus collapse, butsome time must elapse before the ionisationlevels have returned to their initial values prior tothe dischargesequence. To allow for deionisation in tube 23 without interruption ofthe pulse recording process, tube 30 takes over until the dischargeseiquence reaches cathode 35', when relay. will operate to isolate tube30 and to reconnect tube 23, and at the same time recording device :49will beadvanced one count. i I

It would of course be possible to extinguish each of the tubes. of Fig.2 by means of 311C011- denser circuit of the type used in Fig. 1, thesecircuits being arranged to transfer the pulses from each tube to theother and temporarilypto reduce the maintaining potential to extinguishthe discharges. With this arrangement :the "constant maintainingpotential could bepermanently connected to both tubes.

Tounderstancl more fully the operation of :the devices illustratedinFigs. 1 and-2 it isprofitable to consider the working of tubes of the.typendescribed in a little more detail. i

If the circuit of Fig. 1 were to be used with a tube having only threedischarge gaps; sequential firing, and a voltage drop forextinguishmentcan be obtained when the cathode surface of'rthe last gapis or thesame dimensions as thezother cathodes;

The level to which ionisation-must be reduced to avoid misfiringof thetube in the next'pulse cycle can be adjusted to some extent by varyingthe dimensions of the gapsaandrcomposition and pressure of the gasatmosphere. For instance,:it can be arranged that the gaps otherthanxthe starting gap require a higher energy level to fire them so thatthey'will not fire out of turn even in the presence of a fair degree ofresidual ionisation.

There is however a limit to the extent to which such measures canbepursuedand a Welldesigned tube-operating on convenient voltages andwithin practical tolerances will already haveexhaust ed suchpossibilities.

.A pulserate such that the interpulse interva doesnot leave time for thedecay of ionisation to proceed to the required level may be applied tothe tube provided that the time constants .of condenser 19 and theresistances l'2eand l5 ar.e chosenso that the voltage across theelectrodes is maintained below the level required to start a dischargein the startinggap .for atime sufficient to allow for ionisation decay.

The efiect of this will be that a pulse orpulses after the onewhichfired the lastgap will fail to raise the inter-electrode voltage tothe firing pointo'f the first gap. The number of pulses missed in thisway: cannot be extended; indefinitely since the recovery of thecircuit'depends onthe recharging of condenser l9 which will followan'exp'onentiallaw and "the definition'of thereoovery point inrelation tothe pulse cycle-cannot in practice be made accurate enough. unless'thepulse to pulse time'interval is substantial in relation to the'circuitrecovery time. Therefore if it is desired to increase the pulse rate toa-point requiring the suppressionof a substantial number of pulses, thearrangementof Fig.2 is-preferable.

As the number of discharge gaps in the tube is increased the problem ofobtaining an adequate voltagedropifrom the discharge in the-last gap toextinguish all the discharges becomes more difficult, and necessitatesresort to means for increasing the current passed in the last gap. Thetube illustrated in Fig. 1 has a larger cathode area for the last gapfor this purpose.

A limit is set to the permissible enlargement of the current in the lastgap, however, because the considerable ionisation arising from thisdischarge tends to lower the discharge maintaining voltage of the gapsby the same extent as it decreases the applied voltage, not onlydefeating the extinction of the discharges but also requiring a longerperiod for the decay of the increased ionisation to the requisite level.

. This sets a limit to the number of gaps which can be used in a tubeconnected in the circuit of Fig. 1, and for larger numbers of gaps thearrangement of Fig. 2 is to be preferred.

It is possible to use more than two tubes in a cascade arrangementsimilar to that of Figure 2.

It is of course possible to apply the principle of the invention inother ways.

For instance an external source of square pulses, synchronised to thedischarge of the last gap of the tube can be applied to the tube inopposition to the standing inter-electrode potential so as to hold thetube inert for the requisite time for deionisation, this time beingarranged to span an integral number of the pulses to be recorded.

A self restoring flip-flop circuit of any suitable type, for instance anEccles-Jordan circuit, could be used for the purpose, connected to theexternal circuit of the last gap so that the discharge in that gaptriggered the flip-flop circuit causing it to produce a quenching pulselasting during the restoring time of the flip-flop circuit.

With such an arrangement the limits to the number of gaps, inherent inthe Fig. 1 arrangement could be extended.

The principal advantage of all these arrangements is to enable a tube ofa given deionising characteristic to record higher pulse rates.

It has already been indicated, however, that a larger counting radix isobtained than the number of gaps in the tube.

This advantage may not be reaped in cases where discontinuous countingis required, owing to the fact that the tube counts to a radix equal tothe number of its gaps on the first pulse cycle applied to it.

When continuous counting is required however, this miscount of the firstcycle is unimportant for certain types of the application, e. g.frequency dividing where phase change is not important, whereas theincrease of the counting radix may give advantages.

The circuit of Fig.1 for instance using an eight gap tube will count toa radix of ten and without a discharge-maintaining potential when theyare used in the manner of this invention provided that the pulseamplitude is raised so that the gaps will fire without the assistance ofthe constant potential.

With such an arrangement a gap, once fired, will extinguish betweenpulses but will re-fire -fr'omthe next pulse provided that theinter-pulse 'interval is not so long that the gas in the said gaps andin the next gap required to be fired by the next pulse does not becomedeionised.

This deionisation will take place and break the sequence of dischargesat low pulse rates, but when the pulse rate is such that the period ofmore than one pulse is required for deionisation, the conditions withwhich this invention is chiefly concerned, the constant potential may bedispensed with. With such an arrangement since the discharge of the tubeas a whole is extinguished by reason of the removal of the last pulse,there is no need to provide special means for this purpose.

Some form of timing means such as an Eccles- Jordan circuit triggered bythe discharge of the last gap would of course still be necessary to timethe period of one or more pulses and for instance open the pulse circuitto the tube for that period.

What is claimed is:

1. A device responsive to recurring pulses of electrical energy whichcomprises a cold cathode gas discharge tube having three or moredischarge gaps arranged sequentially to fire in succession in apredetermined order on the application of pulses to the said gaps incommon, ionisation from the discharge in one gap lowering the voltagenecessary to fire the next adjoining unfired gap and so priming the saidadjoining gap, means for applying pulses to said gaps, means forautomatically extinguishing all discharges in the said gaps when all thegaps have been fired in turn and for preventing one or more pulsesimmediately succeeding the pulse which caused the last of the said gapsto fire from firing any of the said gaps in the tube in order to providetime for all the said gaps in the tube to extinguish and to deionise toat least a predetermined extent so that the next pulse allowed to affectthe tube will fire the first gap in the said predetermined order and noother gap.

2. A pulse responsive device arranged to respond to successive cycles ofpulses of a predetermined number comprising a cold cathode gasdischargetube :having a number of discharge gaps arranged sequentially to fire insuccession on the application of pulses to the said gaps in common, thenumber of the said gaps being less than the number of pulses in anapplied cycle, means responsive to the discharge in the last gap forcounting the remainder of the pulses of a cycle after all of said gapshave fired once and means for preventing operation of the tube by thesaid remainder pulses.

3. A device, as claimed in claim 1, in which the last mentioned meanscomprises another tube or tubes similar to the first mentioned tube, andmeans responsive to the discharge in the last gap of said first tube forcausing the gaps of said other tube to fire in sequence from pulsesimmediately succeeding that which fired the last gap of the firstmentioned tube, and means for preventing pulses from firing gaps of thefirst mentioned tube during the discharge sequence of the said othertube.

4. A device as claimed in claim 3 in which means is provided forextinguishing the discharge in the said other tube when all gaps havefired and for causing the firing of the said selected gap of the firstmentioned tube by the next pulse received and starting a sequence ofdischarges therein.

5. A device, as claimed in claim 1, in which a source of constantpotential is connected across all the said gaps in the tube, suchpotential being insufiicient to initiate a discharge in the said gapsbut sufficient to maintain a discharge, once initiated, and the meansfor extinguishing all discharges in the said gaps on or after firing ofthe last of the said gaps in the said predetermined order comprisesmeans for reducing said. potential.

6. A device, as claimed in claim 5, in which the means for extinguishingthe said gaps and for preventing one or more succeeding pulses fromaffecting the tube, comprises a condenser connected in parallel with theelectrodes of the last gap of the said tube, the condenser beingnormally charged by potentials applied to said electrodes, and beingadapted to discharge on the firing of the last gap, whereby thepotential applied to all the gaps of the tube is maintained below thatnecessary to fire any gaps in the tube and is maintained at that levelso long as the charge in the said condenser remains below apredetermined level.

7. A device, as claimed in claim 1, in which a source of constantpotential is connected across all the said gaps in the tube, suchpotential being insufficient to initiate a discharge in said gaps butsufficient to maintain a discharge, once initiated, and the means bothfor extinguishing the said gaps and for preventing a succeeding one ormore pulses from affecting the tube, is a resistance in series with theconnection to one electrode of all gaps in the tube adapted to fire insuccession, the increased current through the said resistance, on thefiring of the last gap of the said tube, causing the potential acrossthe said gaps of the tube to fall below that required to maintaindischarges in the said gaps.

8. A device, as claimed in claim 1, in which the last mentioned meanscomprises another tube similar to the first mentioned tube, and meansresponsive to the discharge in the last gap of said 4 first tube forcausing the gaps of said Other tubes to fire in sequence from pulsesimmediately succeeding that which fired the last gap of the firstmentioned tube, and means for preventing pulses from firing gaps of thefirst mentioned, tube during the discharge sequence of the said othertube, said means including a constant source of potential which whenapplied to all the gap in the tube is insufiicient to initiate adischarge in said gaps, but suflicient to maintain a discharge, onceinitiated, and means for connecting said potential to the tubes in turn,said means being responsive to the discharge of the last gap in each ofthe tubes for disconnectin said potential from that tube and connectingit to the other.

9. A device as claimed in claim 8 in which the means for connecting anddisconnectinga source of potential simultaneously with the connectionand disconnection of the pulse applying means to said tubes aredisconnected from a tube at the same time as the said constant potentialis disconnected.

10. A device, as claimed in claim 1, in which a source of constantpotential is connected across all the said gaps in the tube, suchpotential being insufiicient to initiate a, discharg in the said gaps,but sufficient to maintain a discharge, once initiated, and the mean forextinguishing all discharges in the said gaps on or after firing of thelast of the said gaps in the said predetermined order comprises meansfor disconnecting the said source of constant potential.

ALEC HARLEY REEVES.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,404,920 Overbeck July 30, 19462,443,407 Wales June 15, 1948

